• Journal of Astronomy and Space Sciences
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• 제33권1호
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• pp.1-11
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• 2016

Over the last few years, the data obtained using the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope has provided new insights on high-energy processes in globular clusters, particularly those involving compact objects such as MilliSecond Pulsars (MSPs). Gamma-ray emission in the 100 MeV to 10 GeV range has been detected from more than a dozen globular clusters in our galaxy, including 47 Tucanae and Terzan 5. Based on a sample of known gammaray globular clusters, the empirical relations between gamma-ray luminosity and properties of globular clusters such as their stellar encounter rate, metallicity, and possible optical and infrared photon energy densities, have been derived. The measured gamma-ray spectra are generally described by a power law with a cut-off at a few gigaelectronvolts. Together with the detection of pulsed γ-rays from two MSPs in two different globular clusters, such spectral signature lends support to the hypothesis that γ-rays from globular clusters represent collective curvature emission from magnetospheres of MSPs in the clusters. Alternative models, involving Inverse-Compton (IC) emission of relativistic electrons that are accelerated close to MSPs or pulsar wind nebula shocks, have also been suggested. Observations at >100 GeV by using Fermi/LAT and atmospheric Cherenkov telescopes such as H.E.S.S.-II, MAGIC-II, VERITAS, and CTA will help to settle some questions unanswered by current data.

• Journal of Plant Biotechnology
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• 제5권1호
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• pp.51-57
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• 2003

Doubled haploids have long been recognized as a valuable tool in plant breeding since it not only offers the quickest method of advancing heterozygous breeding lines to homozygosity, but also increased the selection efficiency over conventional procedures due to better discrimination between genotypes within any one generation. Salt tolerant mutants were obtained in rice the variety, 'Hawsungbyeo', through in vitro mutagenesis of in vitro cultured anther-derived calli. Various doses (30, 50, 70 and 90 Gy) of gamma ray were applied to investigate the effect of radiation on callus formation on medium containing 1% NaCl, green plant regeneration, frequency of selected doubled haploid mutants and of the salt tolerant screen. It was demonstrated that the dose of 30 and 50 Gy gamma rays had significant effects on callus formation, regeneration and selection of salt tolerance. No tolerant lines were obtained from non-mutagenized cultures. From gamma ray irradiated cultures, five tolerant lines ($M_2$generation) at germination stage and 13 tolerant lines ($M_3$genoration) at seedling stage were obtained. The frequency of salt tolerant mutants indicates that anther culture applied in connection with gamma rays is an effective way to improve salt tolerance.

• Journal of Plant Biotechnology
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• 제46권2호
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• pp.88-96
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• 2019

Terpenes constitute a large class of secondary metabolites in plants. The Oryza sativa terpene synthase is a vital gene in plant defense response. In this study, the molecular and physiological functions of Oryza sativa terpene synthase 30 (OsTPS30, LOC_Os08g07080) were investigated after exposure of the seeds and plants to gamma-rays. The OsTPS30 expression was slightly induced at 200 Gray (Gy), but was significantly induced at 400 Gy. The total terpenoid was synthesized more in OsTPS30-overexpressing (OX-OsTPS30) Arabidopsisthaliana plants than in wild-type (WT) plants. The OX-OsTPS30 plants exhibited resistance to gamma-rays, as compared to WT. The OX-OsTPS30 plants had significantly increased height and weight after gamma irradiation. Additionally, the activity of antioxidant enzymes was increased more in OX OsTPS30 plants than in WT plants after gamma irradiation. Furthermore, the OsTPS30-GFP fusion protein was mostly localized in the chloroplast, suggesting that OsTPS30 is putative MEP pathway-related terpene synthase.

• 한국정보통신학회논문지
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• 제16권10호
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• pp.2323-2328
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• 2012

전 세계적으로 해운물류 안전 보안체계가 강화됨에 따라 국가물류보안 체계 구축을 위한 유비쿼터스 기술 기반의 해운물류 안전 보안 핵심기술 개발이 이루어지고 있다. 현재까지의 U-기반 해운물류 안전보안 시스템 개발과 관련하여 X-선을 이용한 3차원 검색장치 즉, 화물검색장치 개발에 대한 핵심기술을 개발해 오고 있고, 추가적으로 감마선을 검출할 수 있는 휴대용 방사선 검출 장치의 개발 필요성이 높아지고 있다. 본 논문에서는 방사선에 의한 인체, 물체 및 공공상의 장해를 미연에 방지하기 위한 고속의 휴대용 방사선 검출 장치 플랫폼 구현에 대한 연구를 제안하고자 한다.

• 한국의학물리학회:학술대회논문집
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• 한국의학물리학회 2002년도 Proceedings
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• pp.123-125
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• 2002

Blue light of Cherenkov radiation generated by electrons in transparent substances such as water and acrylic resin is well known generally. If students can easily observe the blue light at school, they may be impressed by the fascinating radiation. Four years ago, management of the Co-60 unit for radiotherapy was transferred to Nagoya University School of Health Sciences from a related hospital. We have examined whether or not the Cherenkov radiation in water from secondary electrons generated by Co-60 gamma-rays can be safely observed by eyes and photographs. First, the Cherenkov radiation in the water tank was led to the corridor outside the irradiation room by a mirror, and observed directly without any effect of the radiation exposure. Second, photographs of the Cherenkov radiation were taken under the conditions consisted of several irradiation fields and pass lengths of gamma-rays in water.

• 공업화학
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• 제5권2호
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• pp.321-326
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• 1994

에테르기를 가진 수용성 포스파젠 고분자를 감마광선에 노출시켜 좋은 수분-팽윤도를 가진 친수성 겔을 만들었다. 이 친수성 겔들의 물리적 강도가 감마광선의 강도에 따라 조절될 수 있었다. 트립신과 수용성 포스파젠 고분자를 함께 감마광선에 쪼여 트립신을 겔의 망 사이로 고정시켰다. 고정된 트립신의 활성도는 N-${\alpha}$-benzoyl-1-arginine-p-nitroanilide와 반응시킨 후 분광학적인 방법으로 조사하였다. 고정된 트립신은 적어도 500시간 후에도 상당히 좋은 활성도 수율과 안정도를 가지고 있었음을 보여주었다.

• 폴리머
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• 제25권2호
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• pp.270-278
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• 2001

의료용 고분자로 널리 알려진 poly(vinylalcohol)(PVA)와 poly(N-vinylpyrrolidone)(PVP)를 이용하여 상처치료용 하이드로겔을 제조하였다. PVP 하이드로겔의 기계적 강도를 향상시키기 위해 PVA/PVP 혼합용액에 \"freezing and thawing (동결융해)\"을 반복한 후 방사선 ($^{60}$Co${\gamma}$-rays)을 조사하여 하이드로겔을 얻었다. PVA와 PVP의 조성비 (30 : 70 ~ 100 : 0), 동결융해의 반복횟수, PVA 분자량을 변화시키면서 PVA/PVP 하이드로겔의 겔화율, 팽윤도, 겔강도를 측정하였다. PVA/PVP 하이드로겔은 방사선 조사로만 제조되었을 때 보다 동결융해 반복 후 방사선조사했을 때 겔화율과 겔강도가 향상되었다. 이외에 동결융해의 반복정도에 따른 물성의 특징을 논의하였다.특징을 논의하였다.

• Nuclear Engineering and Technology
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• 제52권10호
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• pp.2387-2393
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• 2020

In this study, a gradient material for shielding neutrons and gamma rays was developed, which consists of epoxy resin, boron carbide (B₄C), lead (Pb) and a little graphene oxide. It aims light weight and compact, which will be applied on the transportable nuclear reactor. The material is made up of sixteen layers, and the thickness and components of each layer were designed by genetic algorithm (GA) combined with Monte Carlo N Particle Transport (MCNP). In the experiment, the viscosities of the epoxy at different temperatures were tested, and the settlement regularity of Pb particles and B₄C particles in the epoxy was simulated by matlab software. The material was manufactured at 25 ℃, the Pb C and O elements of which were also tested, and the result was compared with the outcome of the simulation. Finally, the material's shielding performance was simulated by MCNP and compared with the uniformity material's. The result shows that the shielding performance of gradient material is more effective than that of the uniformity material, and the difference is most noticeable when the materials are 30 cm thick.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 광주전남지부
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• pp.87-90
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• 2006

Two SiC radiation detector samples were irradiated by Co-60 gamma rays. The irradiation was performed with dose rates of 5 kGy/hour and 15 kGy/hour for 8 hours, respectively. Metal/semiconductor contacts on the surface were fabricated by using a thermal evaporator in a high vacuum condition. The SiC detectors have metal contacts of Au(2000 ${\AA}$)/Ni(300 ${\AA}$) at Si-face and of Au(2000 ${\AA}$)/Ti(300 ${\AA}$) at C-face. I-V characteristics of the SiC semiconductor were measured by using the Keithley 4200-SCS parameter analyzer with voltage sources included. From the I-V curve, we analyzed the Schottky barrier heights(SBHs) on the basis of the thermionic emission theory. As a result, the 6H-SiC semiconductor showed- similar Schottky barrier heights independent to the dose rates of the irradiation with Co-60 gamma rays.

• Nuclear Engineering and Technology
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• 제54권1호
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• pp.262-268
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• 2022

This paper introduces a novel concept of the pulsed neutron facility (PNF) for maximizing the production of the thermal neutrons and its application to medical use based on prompt gamma neutron activation analysis (PGNAA) using Monte Carlo simulations. The PNF consists of a compact D-T neutron generator, a graphite pile, and a detection system using Cadmium telluride (CdTe) detector arrays. The configuration of fuel pins in the graphite monolith and the design and materials for the moderating layer were studied to optimize the thermal neutron yields. Biological samples - normal and cancerous breast tissues - including chlorine, a trace element, were used to investigate the sensitivity of the characteristic γ-rays by neutron-trace material interactions and the detector responses of multiple particles. Around 90 % of neutrons emitted from a deuterium-tritium (D-T) neutron generator thermalized as they passed through the graphite stockpile. The thermal neutrons captured the chlorines in the samples, then the characteristic γ-rays with specific energy levels of 6.12, 7.80 and 8.58 MeV were emitted. Since the concentration of chlorine in the cancerous tissue is twice that in the normal tissue, the count ratio of the characteristic g-rays of the cancerous tissue over the normal tissue is approximately 2.